FIG. 1 illustrates ICs 10 and IC pins 12 mounted upon leadframe 14. ICs are mounted in this fashion after a typical plastic encapsulation process and prior to undertaking trim and form processes. The purposes of trim and form machinery are to 1) trim off the excess plastic and metal, and 2) form the IC pins into their final shapes.
FIG. 2 illustrates an exploded detailed portion of two Ics 10 and particular portions of leadframe 14 comprising the following elements: railings 16, bridge 18, dambars 20, and windows 22, 24 and 26.
A typical Trim process often incorporates, in some selected order, the following steps: The encapsulating plastic scrap must be removed, this is usually called deflashing. Plastic is typically located in the window regions 22, 24, 26 and on areas of the lead frame. The dambars 20 must be removed or cut away to connect windows 22 and 24, and to isolate pins 12 from each other. The bridges 18 are removed to further isolate, pins 12 from other IC pins. FIG. 3 illustrates what an IC would look like after a typical trim processes.
It is noted that some manufacturing processes do include an electroplating step after or in-between two of the trim processes. An electroplating process is a sophisticated way of adding solder to the pins of the IC in preparation for later welding of an IC to a circuit board.
After the Trim processes take place, there are Form processes. Form processes mold or shape the IC pins into their final shapes. One particular pin shape or form is called the `DIP` shape, which is short for "dual in line pins." The remainder of the invention disclosure will refer to this pin form, although many other forms are well known in the art and are easily adapted for use of this invention.
FIGS. 4a-c illustrate a three step DIP forming process. IC pins 12 start out straight, are then partially bent, and then bent to the full vertical final form.
One skilled in the art will recognize that the pin forming processes take place while the ICs are still attached to the rails 16 of the leadframe 14. Thus, a typical first step after the pins have been formed is to separate the ICs from the leadframe railings 16, typically called a singulation process.
FIGS. 5a-c illustrates a typical forming machine tool or bit set used for bending the un-bent pins in FIG. 4a into the transitional shape illustrated in FIG. 4b. There is an anvil 30, a punch 32, and pressure pad 34. One skilled in the art will understand that there may be any number of pin forming stations and having any number of configurations for the anvil, punch, and pad that may be required for the pin forming processes; especially for more complex pin shapes than are illustrated.
In operation, and in reference to FIG. 5a, anvil 30 is usually fixed in place and pin 12 rests upon it. Pressure pad 34 moves to hold or clamp the pin in position. In reference to FIG. 5b, punch 32 has moved to engage and thereby bend the pin to the designed configuration.
FIG. 6 illustrates a representative portion of a trim and pin forming machine. One can purchase such a machine from ASM Asia Inc., 4302 E. Broadway Rd., Phoenix, Ariz., model AP50. FIG. 6 has the following elements: top platen 40, vertical action rod 42, table 44, IC loading station 50, trim stations 60, forming stations 70, and singulation station 80. Trim stations encompass: deflashing station 62, dambar removal station 64, and bridge removal station 66 (also referred to as a station for pin/lead cut or trim to length). Forming station 70 encompasses: a first forming station 74 (illustrated in FIG. 5A and B), and a second forming station 76 (for creating the form illustrated in FIG. 4c). There is also a conveyor system for moving the ICs 10, which are attached to leadframe 14, in a linear order, to each work station.
In operation, all processes or work station activities take place on a paced operation which is timed to the platen's 40 up and down cycles. When platen 40 is up, the conveyor system will move the leadframe/s forward, readying the ICs for their next step of operation or simply loading new leadframes in preparation for the assemble process. When the platen 40 is "punched down", the various work stations perform their various designed operations, cutting, shaping, cleaning, etc. Table 44 usually does not move, yet holds the anvils as shown in FIG. 5. Platen 40 typically holds the punch 32 and pad 34 as shown in FIG. 5.